1. Field of the Invention
This invention relates to elastomeric copolyesterethers based on poly(1,4-cyclohexanedimethylene 1,4-cyclohexanedicarboxylate) modified with polytetramethylene ether glycol which may be extrusion blown into objects such as clear flexible bags or film.
The ability to be blow molded results largely from high melt strength. A polymer having good melt strength is described as one which can support its own weight in the molten state after being extruded from a die. When a polymer without good melt strength is melt extruded downward from a die, the melt rapidly drops and forms a thin string or breaks. Such polymers are not useful for extrusion blow molding objects. When polymers have sufficient melt strength they can be extruded downward in the shape of a hollow cylinder. Containers can be formed by clamping a mold around a molten hollow cylinder (which has been extruded) and subjecting the hollow cylinder to internal pressure to form the bottle, a practice which is well known to those skilled in the art.
2. Background Art
Copolyesterethers derived from 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol and polytetramethyleneether glycol are known in the art. U.S. Pat. Nos. of interest include No. 4,003,882 to Fagerburg et al; 3,261,812 to Bell et al, 3,023,192 to Shivers; 4,221,703 to Hoeschele; and 3,651,014 to Witsiepe. Also, copending Ser. No. 106,963 of Davis et al, and now U.S. Pat. No. 4,256,860, issued Mar. 17, 1982 relates to such copolyesterethers derived from polypropyleneether glycol. It is not believed to have been known in the art, however, that if such copolyesterethers are derived from 1,4-cyclohexanedimethanol and 1,4-cyclohexanedicarboxylic acid having high trans isomer contents within a particular range, modified with polytetramethyleneether glycol of a molecular weight within a certain range and in certain amounts, and containing a branching agent, the desirable properties described herein for the present invention would be achieved.